Раст простейший "Hello World"

$ rustup --help
rustup 1.23.1 (3df2264a9 2020-11-30)
The Rust toolchain installer
 
USAGE:
    rustup [FLAGS] [+toolchain] <SUBCOMMAND>
 
FLAGS:
    -v, --verbose    Enable verbose output
    -q, --quiet      Disable progress output
    -h, --help       Prints help information
    -V, --version    Prints version information
 
ARGS:
    <+toolchain>    release channel (e.g. +stable) or custom toolchain to set override
 
SUBCOMMANDS:
    show           Show the active and installed toolchains or profiles
    update         Update Rust toolchains and rustup
    check          Check for updates to Rust toolchains
    default        Set the default toolchain
    toolchain      Modify or query the installed toolchains
    target         Modify a toolchain's supported targets
    component      Modify a toolchain's installed components
    override       Modify directory toolchain overrides
    run            Run a command with an environment configured for a given toolchain
    which          Display which binary will be run for a given command
    doc            Open the documentation for the current toolchain
    man            View the man page for a given command
    self           Modify the rustup installation
    set            Alter rustup settings
    completions    Generate tab-completion scripts for your shell
    help           Prints this message or the help of the given subcommand(s)
 
DISCUSSION:
    rustup installs The Rust Programming Language from the official
    release channels, enabling you to easily switch between stable,
    beta, and nightly compilers and keep them updated. It makes
    cross-compiling simpler with binary builds of the standard library
    for common platforms.
 
    If you are new to Rust consider running `rustup doc --book` to
    learn Rust.